1. Field of the Invention
This invention relates, in general, to a modular bridge structure and more particularly, to a modular type platform mountable like a bridge between vertically movable suspended stagings wherein like configured bridge units are interconnected end to end to form a flexible staging platform.
2. Description of the Prior Art
In the past, staging platforms have usually been constructed as a single rigid longitudinally extending unit supported near its ends or also at spaced points between its ends from hanging cables. U.S. Pat. No. 2,916,102 discloses a pair of one piece rigid bridge structures pivotally connected end to end, the central pivot point necessitating use of a central support cable to prevent the staging platform from sagging at its center. U.S. Pat. No. 2,041,031 also discloses a joint for interconnecting two scaffolds end to end, the interconnected scaffolds again being supported both centrally and at its ends by vertically extending cables.
The old U.S. Pat. No. 175,095 discloses a painter's scaffold having a deck or platform which is stiffened by brace rods which are stated to be of considerable strength and which extend longitudinally beneath the platform and are connected thereto near its ends.
Staging platforms which are incrementally length adjustable by extending sliding deck pieces longitudinally from beneath the ends of a central deck structure are also known as are platforms whose lengths may be varied by the addition or substraction of entire platform sections which are rigidly clamped together. Platforms of these types are presently offered for sale by Spider Staging, Inc. of Renton, Washington.
In the past, it has been thought necessary for safety reasons to construct staging platforms to be structurally rigid, rigidity generally having been equated with strength. In use, however, these rigidly constructed platforms are relatively easily damaged such as by being inadvertently lowered onto an obstacle causing a portion of the platform substructure to be bent and weakened, or if the obstacle happens to be located near the longitudinal center of the platform, causing the entire platform to be bowed thereover thereby unduly stressing the entire platform structure. Further, known rigid platform structures are particularly unsuited to withstand longitudinal twisting forces or torsional forces such as those encountered when a corner of such a platform catches on an outwardly projecting portion of a building during raising or lowering of a platform, or when a platform is lowered onto the ground with an obstacle under one corner of the platform.
Further, replacement of bent or broken structural members of known types of staging platforms often necessitates the platform being returned to the manufacturing plant causing the platform to be out of service for a substantial period, often just when it is most needed at a construction site or the like.